Two cycle engine



y 1932- J c. G. CURTIS ET AL 1,858,002

TWO-CYCLE ENGINE Filed July 2, 1930 3 Sheets-Sheet 1 EARLE R. BY.

MaLylO, 1932 v c. G. CURTIS ET'AL I 1,858,002

. g l v TWO-CYCLE ENGINE Filed Jul 2, 1950 :5 sheets-sheet 2 y 1932- c. e. CURTIS, ET AL 3, 0 TWOQCYCLE ENGINE y Filed July 2, 1930 fishee'ts-shelet .'5'

WORNEY Patented May 10, 1932 UNITED STATES PATENT orrlcs owns a. comma, or new roux, am) mm a. imw'ron. or Jamaica, NEW YORK 'rwo cram ENGINE Application filed July 2, 1980. Serial No. 465,269.

This invention relates to two-cycle port scavenged engines and provides improvements therein. The invention provides means for creating the turbulence necessary for good combustion, for insuring a high scavenging efiiciency, and, if desired, a supercharge within the cylinder. Turbulence and high scavenging efliciency are vital factors, particularly in high speed engines.

To obtain the maximum scavenging efiiclency using a minimum of air at a low pressure we use skew air inlet ports, that is, ports turned backward to direct air streams back toward the inlet sides of the cylinders in such amanner that air streams oppose each other and cause a flow of air from the region of the piston head up to the cylinder cover generally on the inletside of the cylinder. The exhaust ports are in the other side of the cylinder wall.

The present invention is an improvement u on the subject-matter of Curtis Patent 1577,827, dated October 7, 1930, Curtis and Newton Patent 1,780,175, dated November 4, 1930, and Curtis and Newton applications Serial Nos. 375,928 and 381,736.

In arrangements having the same number of inlet air ports on either side of a center line, with the angles of the correspondmg opposingports the same, the areas of the correspondmg opposing ports the same and the scavenging pressure supplying the opposing ports uniform, the air flows from the region 1 of the piston head, up on the inlet side of the cylinder to the cylinder cover and down the opposite side, or exhaust port side, of the cylinder without rotation circumferential to th cylinder. By the present invention we propose to upset the normal balance of an arrangement such as just referred to in such a manner and to such a degree as to cause to be set up a circumferential rotation of the air within the cylinder without seriously marring the high scavenging efliciency normally resulting from the use of such a skew port arrangement, maintaining all the inlet ports in a single transverse plane.

. The invention also provides for the circum.

ferential rotation of the air being caused to I occur at a desired time.

The invention further provides means whereby in an engine having exhaust ports of greater height than the inlet ports, the engine compression may be begun simultaneousllyl with the cutting oil of the inlet ports by t e piston on its compression stroke.

These desired results may be accomplished m various ways and, in Figs. 1, 2, 3 and 4 of the drawings, we have illustrated some of the embodiments. However, the invention may be carried out in other ways and the selected embodiments in no way limit its scope.

Figs. 1, 2 and 3 are horizontal sections diagrammatic) through the port region of t e cylinder of a two cycle port scavenged engine. Fig. 4 is a similar horizontal section and Fig. 5 is a diagrammatical elevation, the section shown in Fig. 4 being on the line A, A Fig. 5, sections F igs. 1, 2 and 3 being at a similar locality. Figures 6, 7 and 8 are vertical sectional views through the inlet port section, the sections being on lines VI VI, VIIVII and VIIIVIII, Figure 1,

' respectively. Fig. 9 is a development of a part of the inside wall of the cylinder 1 on the inlet-port side, related to Fig. 2, and showing the greater area of the inlet-ports L shown at the left, as compared with the area of the inlet-ports R shown at the right in said figure.

The engine cylinder 1 has air'inlet ports 2 and exhaust ports 3, both near the piston end of the cylinder and in opposite sides of the cylinder wall. They are uncovered and covered by the movement of the piston 4. The inlet ports 2 are supplied in the usual manner with compressed air from a source not shown through the intermediary of an air belt 5. Similarly, the exhaust ports 3 deliver into an exhaust belt 6.

In the embodiments selected for illustration, Figs. 1 to 4 inclusive, the air inlet ports are shown as forming a substantially continuous bank extending-a little more than half 1 port are each 45. Figure 6 is a longi- \tudinal section showing the middle port at an inclination of 60; Fig; 7 "shows an ad jacent port at an inclination of 45; and Fig. 8 shows an end port-approximately horizontal. In Fig. 3 the M ports are given a tangential direction and they are progressive in longitudinal obliquity; the left hand one is 40, the middle one and the right hand one If these middle. ports M are omitted, as.

they may begtheinlet portarea is reduced, necessitating a higher scavenging air pressure and hence a poorer. overall enginc efiiciency. The scavenging efliciency, however,

is not seriously affected. y

In the following description of the illustrated embodiments, the features pertinent to the invention are adequately setforth but the operation of the two-cycle engine is well w is directed toward the L ports.

known and hence not described.

In Fi 1 the L ports are of the same area as the ports, both are horizontal or approximately horizontal and corresponding ports in the L and R groups are turned back through the same angles. The M ports are symmetrically arranged and are longitudinally oblique and of the same height, measured on the cylinder wall, and'are in the same transverse plane as the L and R ports. The compressed air flowing into the air belt 5 The velocity is partially converted into pressure and causes a building up of the pressure at the L port end of the air belt; that is, P is greater than P and the drop in pressure through the L ports is greater than through the R ports and the L ports will pass more air at a correspondingly higher velocity. A counter-clockwise rotation is set up. At the time scavenging begins, that is, when the air inlet ports first open, the pressure in the .air-

belt is uniform and scavenging begins in the normal manner with P and P approximately equal. This is followed by a building up of P and a lowering of P which sets up the rotation at the desired time.

In Fig. 2 the pressuresP and P remain approximately equal due to admitting the air to the air belt 5 normally. The L ports are given a greater area than the R ports (as shown in Figs. 2 and 9) and hence carry more air and set up a counter-clockwise rotation during the whole admission period.

In Fig. 3 the pressures P and P are maintained approximately equal and the L ports and R ports are of the same area. The longitudinally oblique M ports are turned to direct their air streams tangentially and u ward toward the cylinder cover. These ports being steeply oblique and the L and R ports more nearly horizontal, as shown in Figs. 6, 7 and 8, the air streams from the M ports climb up over. the streams from the L and ports without direct intermixturene'ar the piston but set the air in rotation as it approaches the cylinder cover end of the cylinder.

In' Fig. 4 the-port arrangement is the skew port arrangement described 'above symmetrically arranged. A choke valve 7 is provided in the air belt 5 which when closed causes the pressure P to exceed P This choke'valve may be open during thebeginning of the scavenging period'as shown in dotted lines, Fig.4, and closed to set upthe rotation during the latter part of the scavenging period,--or during the ,supercharging. period, if any, which follows the scavenging period, as shown in full lines, Fig. 4.

A permanent choke may be substituted for the timed choke valve. causing an operation in effect very similar to that described in refer-- ence to Fig. 1.

In Figs. 4 and :5 are also shown a. piston during the early part of the scavenging period v and to clplse during the latt er part of this period, being closed at the same time as, or

before, the engine piston cuts off the air inlet ports, thus insuring a superatmospheric pressure charge in the cylinder and along engine compression stroke beginning at the closing of the inlet ports instead of at the closing of the exhaust ports as usual. The choke valve 7 and the exhaust valve 8 may be linked together in any known manner and made to operate in unison, that is, open together and close together, or in any desired time relation.

The invention including means for producing turbulence in a two-cycle engine with skew inlet ports is more broadly claimed in our application Serial No. 381,736.

Having thus fully illustrated and described the features of the invention, we claim:

1. A two-cycle internal combustion engine, comprising a cylinder, air inlet ports comprising two sets of ports arranged to direct opposing streams back toward the inlet side of the cylinder, and means for intensifying the effect of the velocity components of the ,comprising a cylinder, a bank of air inlet ports on one side of the cylinder, exhaust ports on the opposite side, the ports at each end of the air inlet bankarmnged to. d

aaaaooa air streams back toward the inlet side of the cylinder, and means increasing the effect of the flow from one side of the bank relative to the other so as to cause the air within the cylinder to rotate.

3. A two-cycle internal combustion engine comprising a cylinder, a bank of air inlet ports on one side of the cylinder, longitudinally oblique ports in the middle portion of the bank, more nearly horizontal ports in the end portions of the bank arranged to direct air streams back toward the inlet side of the cylinder, and means increasing the effect of the flow from one side of the bank relative to the other so as to cause the air within the cylinder to rotate.

4. An engine according to claim 1, wherein the area of the inlet ports on one side is greater than those on the other side.

5. .An engine according to claim 1, wherein the inlet ports on one side are provided with higher pressure air than those on the other side. I

6. An engine according to claim 1, further including means for choking the free flow of air to the ports on one side.

7. An engine according to claim 1, further including a valve for choking the free flow of air to the ports on one side, said valve being movable for the purpose described.

8. An engine according to claim 3, wherein the longltudinal oblique middle ports direct their air streams tangential to the longitudinal axis of the cylinder.

9. An engine according to claim 1, further comprising an exhaust valve and valve operating means adapted to operate said exhaust valve so as to be open during the early part of the scavenging period and to choke the exhaust flow before the air inlet ports close.

In Witness whereof, we have hereunto signed our names.

CHARLES G. CURTIS. EARLE R. NEWTON. 

